Taking your wastegate signal after the TB causes the turbine to fight against the exhaust flow leaving the head; efficiency drops significantly. This was discussed some in earlier post in this thread.
This is offensive to both Englishmen and Irishmen.

The English would argue that they are not always drunk, and the Irish would argue that they are a more fitting exemplary drunk and should have been chosen as your original example.

 

Cruising speed at 0psi? Wheres ur vac/boost gauge connected? You should be at -15 to -10 tops at cruise.

2l per 10km = roughly 11 miles to the gallon, you should be at ~20miles/gallon for city and 28ish for highway only.

~20mpg=1.2l/10km

 

I would just like to say that I am truly sorry if I offended any british citizens throughout the world.

She swallows like a $20 crack hoe.

 

Ok, I have an 11psi spring taking WG signal from the compressor housing. The car makes 11psi or 184kpa (I think) from the signal at the manifold every time, like clock-work; will moving the WG signal to the cold side of the intercooler give me any increase in pressure? It sounds to me like it won't and like there is not a measurable pressure drop with the BEGi FMIC.

I have a huge BEGi FMIC, FYI.

I'd like to pick up 1-2psi without jacking with a boost controller.

 

You will pick up boost directly proportional to the pressure drop through the IC core.

 

notice the last sentence of the first paragraph. What is a reasonable pressure drop in my intercooler? I fear that it's going to be a negligible increase.

 

imo its something small like half to a little under 1 psi. I wouldn't bother esp since you're not tapering up top.

I dunno why you wont use an mbc. It will definitely help you broaden your torque curve to the left.

 

Thanks

It's already making 90% of max torque at 3500rpm. I don't think adding it to a high quality external gate makes much of a difference. It's making the target 11psi at 3300rpm.

I can't find a boost controller with large enough ports. These wastegates act funny when you put the small vacuum lines on them, I need one with bigger barbs.

Edit: It just dawned on me that I can probably get away with running a small vac line to the secondary chamber on the wasteage since it only needs to see ~2psi...but I'm not sure how much of a difference that line will make in regards to filling the large canister.

 

Doesn't this totally ignore the function of a Diverter/Bypass valve? When the signal line from the manifold to the DV has less pressure than the charge air side of the DV it will vent; correct?

 

Dont most valves require at least 15hg.in vac? Even then your turbo would be fighting against the valve instead of simply opening up the wastegate creating much more efficient way out for the exhaust gasses.

 

I'm not claiming it to be as efficient, I just did not see any mention of DVs.

"Push type" valves do not require vacuum to open just a pressure differential > spring preload.


I have the in and out swapped (input opposing signal line).

"Pull type" valves solely open with vacuum


In a few weeks I plan on measuring the differential at part throttle in my Audi (I5, T3/T3, 034 SEMS) with the WG teed off of the DV line.

 

That's an interesting question.

I don't think that it totally ignores this effect, though the degree to which it is quantifiable begs some thought. I'm thinking along two different and unrelated lines here:

1: Yes, the bypass valve operates via a pressure differential. The question, of course, is what magnitude of difference is required to open it? If we consider the the circumstances surrounding the conventional function of the valve (to bypass the compressor during a shift) at the exact instant of a shift, then we observe the following conditions:The point here is that at the moment of a shift, which is when we expect the bypass valve to open (and is the condition for which we adjust the valve to open) the differential between manifold pressure and pressure at the valve is at least 30 PSI, maybe a great deal more than that. (It would be interesting to datalog this.)

So, in a best-case scenario, if we look at the bypass valve as a relief valve, the effective target compressor pressure is going to be double the actual target map, for a PR of at least 3, and maybe 4. Look at a compressor map for a GT2560 or 2871 and tell me what the compressor efficiency is at that point.



2: Assume that I'm totally wrong about everything above, and that the bypass valve somehow knows to vent at exactly 15 PSI above atmospheric. It's magic. Well, if the wastegate is referenced to manifold pressure, and manifold pressure is being artificially depressed below the wastegate pressure by holding the throttle partially closed, then while the magic bypass valve will in fact prevent pressure in the intake tract from rising above 15 PSI, it will be flowing a tremendous volume of air in order to do so. Again, look at the compressor map, and look at when happens when you double or triple the mass of air being flowed for a given PR.



Either way, compressor efficiency tanks, and the fact that the turbine isn't being bypassed by the wastegate means that exhaust backpressure skyrockets. Heat, heat, and more heat.

 

Good points. I am not so interested in right or wrong and the only reason this is in my head is because I teed off of my DV signal line at ~2am in order to get back on the road

I have a drill and the fitting to tap into my charge air lines so at this point I am just playing.

I can tell you right now that the pressure delta required to vent is <7psi since that is my maximum boost. Log showing DV reactivity (the WG signal in this log is connected to the compressor).

I'll be out of town next week so it will be a bit before I have anyway to log the delta between charge air and IM at part throttle. Unfortunately, I only have one MAP sensor that I can log.

 

I just love the way you tend to open my eyes from time to time.
**** Obama, I would have voted for you!

 

Theres also the forge dump valves that are different than that and they SUCK. I get all kinds of boost surge at nice driving. Simply there isnt enough pressure to force the plastic valve open.

 

I don't know which one you're using, but my forge is working flawlessly and I haven't had a single instance of surge even after swapping to the stiffer (5-15psi) spring.

 

It is exactly like the one in the diagram above.



The problem is the plastic valve is there to prevent air from flowing in in vac. However in my opinion the plastic valve spring is too strong. From what i can tell the big spring is what gets replaced with the stiffer ones for different boost levels however there is nothing mentioned about the small spring..

 

I was wondering whether you managed to find a solution as I've got a very similar steep drop after 4k revs.

 

Tapping the coldside for my signal has helped my problem, but it has not eliminated it. I still drop about 3 psi from peak to redline. I have a hybrid msm turbo with an EVOIII 16G compressor and TD05 hotside. Tuner thinks that it's possible that my continued spike is due to the smaller hotside housing of the msm turbo.

 

eh wth since we're talking about this here i'll toss what i got.

See the small spring? This is my replacement, you can see very thin. That was my problem. The original was too strong so during low loads it would hold the bov down even if the heavy spring on the bottom is fully retracted so the air would have to force the small spring open. Was alright at full boost but at anything less i got surges.




Here is what i did with the holes. Sound now is more of a husss than a whistle it originally made.



The only time this bov leaks is while cruising at about 60-70kpa as the turbo is spooled just enough to force the little spring open and the big spring isnt fully closed yet.

At wot there is no leaks since the big spring now shuts closed and forces the white plastic valve closed with its force.